The invention relates generally to wave soldering of surface mount devices to a printed circuit board, and more specifically to the size and configuration of the solder pads when a surface mounted device is oriented on a printed circuit board with its axis parallel to the direction the circuit board moves through a wave soldering machine.
Prior art wave soldering of a surface mount device (SMD) on a printed circuit board involves mounting the device with its contact ends on equally sized solder pads. The solder pads and SMD are oriented such that the axis of the SMD is perpendicular to the direction that the PC board will pass over the solder wave in a wave solder machine. This placement allows each end of the SMD to directly receive molten solder without the SMD blocking the flow of solder which would otherwise prevent the deposit of solder on the blocked pad.
An important aim in the design and layout of printed circuit boards is to minimize their size. Therefore, components must be packed together in the most efficient way possible. The requirement to orient all SMDs perpendicular to the wave-solder direction has limited packing efficiency in the prior art. Thus, it is very desirable to allow placement of an SMD with any orientation and with a sufficient amount of solder being deposited on each solder pad by wave soldering.